The present invention relates to a sealing device for rolling bearings.
In particular, the present invention may be advantageously applied in the field of rolling contact bearings which are provided with a device for reading functioning kinematic parameters and which is defined by a rotating encoder and a fixed sensor which faces the encoder.
In the above application, and as is schematically illustrated in FIG. 5 labelled “Prior Art”, sealing devices of a well known type comprise a shield 10 which is made of metallic material and which may be installed onto an outer race 11 of the bearing 12, and a sealing lip 13, which starts from the shield 10 in order to be arranged in such a way as to abut an inner race 14 of the bearing 12 itself.
The shield 10 comprises, in turn, a cylindrical lateral wall 15 which is radially interposed between the encoder 16 and the sensor 17, and a frontal shaped wall 18, which is integral with the lateral cylindrical wall 15, and which axially folds inside the lateral cylindrical wall 15 itself in order to further protect the encoder 16, and support the sealing lip 13.
In the above-described sealing devices, with the aim of reducing to a minimum any possible interference concerning the reading of the sensor 17 due to thickness of the lateral cylindrical wall 15 and also due to the metallic material of which it is made, the lateral cylindrical wall 15 presents a passing window 19, which is partially engaged by the sensor 17, and is sealed by a sealing membrane 20 which is made of rubber material.
The membrane 20 is suitable for substantially entering in contact with the sensor 17, and is part of a coating 20′ made of rubber material which is arranged in such a way as to completely cover the shield, and which is made in a single piece with the sealing lip 13.
As is well known, sealing devices protect rolling bearings against the infiltration of impurities, and they also prevent the escape of any lubricating grease from inside the bearings themselves, and they are also subject to dynamic stress due to the difference in pressure between the inside and the outside of the bearings which is caused by the assembly of the bearings, as well as by temperature changes during the functioning of the bearings.
This dynamic stress acts above all on the sealing membrane, which consequently becomes weakened over time, and which, in a worst case scenario, may tear and cause lubricating grease to escape from inside the bearing and thus reduce the bearing's useful working life.